Multiple speaker enclosure with single tuning

ABSTRACT

A combination of a plurality of high compliance speakers and a rigid single tuned enclosure. The speakers are mounted on different walls at one end of the tuned enclosure, and all of the speakers have their low frequency response augmented by the loading effect of the enclosure. The tuned enclosure has a folded path which is substantially equal to one-quarter of the wave length of the in-air resonance of the speakers. The enclosure is open-ended and has a cross sectional area which is substantially equal to the cross sectional area of the cone of one of the high compliance speakers. The enclosure walls are lined with a sound absorbing medium. By this arrangement sound may be effectively dispersed without employing a high volume speaker enclosure.

[ 1 Aug. 29, 1972 Primary Examiner-Stephen J. Tomsky Attorney-Hill,Sherman, Meroni, Gross & Simpson [57] ABSTRACT A combination of aplurality of high compliance speakers and a rigid single tunedenclosure. The speakers are mounted on different walls at one end of thetuned enclosure, and all of the speakers have their low frequencyresponse augmented by the loading effect of the enclosure. The tunedenclosure has a folded path which is substantially equal to one-quarterof the wave length of the in-air resonance of the speakers. Theenclosure is open-ended and has a cross sectional area which issubstantially equal to the cross sectional area of the cone of one ofthe high compliance speakers. The enclosure walls are lined with a soundabsorbing medium. By this arrangement sound may be efl'ectivelydispersed without employing a high volume speaker enclosure.

6 Claims, 2 Drawing Figures [58] Field ofSearch...........................181/3l R, 31 B John Virva, Chicago,Ill.

[73] Assignee: Admiral Corporation, Chicago, Ill.

[22] Filed:

WITH SINGLE TUNING July 6, 1970 Reierences Cited UNITED STATES PATENTSFOREIGN PATENTS 0R APPLICATIONS United States Patent Virva [54] MULTIPLESPEAKER ENCLOSURE [72] Inventor:

21 Appl.No.: 52,164

51 Int.

MULTIPLE SPEAKER ENCLOSURE WITH SINGLE TUNING BACKGROUND OF THEINVENTION 1. Description of the Prior Art My co-pending patentapplication Ser. No. 847,791, filed Mar. 4, 1968 now US. Pat. No.3,523,589 and entitled High Compliance Speaker And Enclosure Combinationrelates to a speaker system having a single speaker mounted in anenclosure which has a cross sectional area approximately equal tothcarea of the cone of the speaker. This arrangement yields excellentperformance and greatly improves the low frequency response as comparedto prior art speaker enclosure combinations. It was believed thatspeaker enclosures should have a cross sectional area approximatelyequal to the area of the cone of the speaker, and accordingly asthe'speaker size increased, the cross sectional area of the enclosureincreased. This rule generally still applies. However, a greatlyimproved dispersal of sound can be obtained by the arrangement of thepresent inventionwherein the same tuned column of air can be used toprovide a loading for more than one speaker mounted at the closed end ofthe column.

2. Field of the Invention The field of art to which this inventionpertains is speaker and speaker enclosure combinations and especially tothe combination of an acoustical open-ended enclosure and a highcompliance speaker having a relatively small volume and an improvedsound dispersal characteristic.

SUMMARY OF THE INVENTION It is a principal feature of the presentinvention to provide a loud speaker system having an improved frequencyresponse and sound dispersal characteristic.

It is another feature of the present invention to provide an improvedcombination of a speaker and enclosure utilizing high compliancespeakers.

It is a principal object of the present invention to provide anopen-ended speaker enclosure for a of high compliance speakers toachieve improved sound dispersal in a room or similar area.

It is another object of the present invention to provide a rigidacoustic enclosure having means for mounting a plurality of highcompliance speakers therein with each of the speakers having a crosssectional area approximately equal to the cross sectional area of thespeaker enclosure.

It is an additional object of the present invention to provide a speakerenclosure for high compliance speakers whichincludes an open-ended tunedcolumn having a length which is approximately equal to onequarter of thewave length of thein-air resonance of the speakers wherein more than onehigh compliance speaker is mounted at the same end of the enclosureoppositely of the opened end and wherein the speakers have their axesdisposed at substantial angles with respect to each other.

These and other objects, features and advantages of the invention willbe readily apparent from the following description of a certainpreferred embodiment thereof, taken in conjunction with the accompanyingdrawing, although variations and modifications may be effected withoutdeparting from the spirit and scope of the novel concepts of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevational view of thespeaker enclosure constructed in accordance with the features of the.present invention prior to the mounting of the speakers therein andomitting the sound absorbing medium. for simplicity.

FIG. 2 is a sectional view of a high compliance speaker enclosureaccording to the present invention showing the positioning of thespeakers in the enclosure and the positioning of the sound absorbingmedium along the walls of the enclosure, and illustrating furtherthefolded character of the tuned column from the speakers to the openend thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention relates toa combination of. a speaker enclosure and a number of high compliancespeakers mounted inthe enclosure to provide an improved frequencyresponse and improved power output without requiring the speakerenclosure to be enlarged to correspond to the combined cross sectionalarea of the speakers.

It has been desired to provide a lower cost speaker system having animproved low frequency sound output, and in addition it has been desiredto provide a speaker system which has a lower physical volume to occupyless space in a room.

My co-pending patent application, Ser. No. 847,791 relates to such asound system. In that application, a single high compliance speaker isshown mounted in a tuned open-ended column which is contrary to theprior teachings of using high compliance speakers in generally sealedvolumes such as is disclosed in the Electronics World article of Aug.1966 beginning on page 25 entitled Enclosures for High Compliance LoudSpeakers by Roger H. Russell. In that article, high compliance speakersare defined as being characterized by heavy magnets, very flexible conesurrounds, long-throw voice coils, and low cone resonance. Thearrangement shown in my co-pending application provides a means forobtaining a higher power output with a lower power input and improvingthe frequency response well below the in-air resonance of the highcompliance speaker.

Previously, it was believed that a larger speaker diameter would requirea larger cross sectional area, and further that the combined crosssectional area of the speaker cones, however many cones were utilized,should approximate the cross sectional area of the enclosure. However, Ihave discovered that by the arrangement of the present invention, animproved sound dispersal can be obtained by using a plurality of highcompliance speakers which have substantially the same in-air resonanceby mounting such speakers in a single enclosure which has a crosssectional area substantially equal to the area of the cone of one of thespeakers.

Referring to the drawing in greater detail, FIG. 1 shows an enclosureaccording to the present invention having a provision for two speakers.The speaker enclosure in FIG. 1 is shown without the sound absorbinglining for simplicity and without the speakers mounted in the respectiveopenings.

The speaker system shown in FIG. I includes an enclosure 10 having a toppanel 11, front and rear panels absorbing medium or the panels may beformed directly of a sound absorbing material such as Tuflex. The panelsmay be riveted together or secured by other suitable means to make thespeaker enclosure substantially rigid.

First and second partitions l7 and 18 are disposed within the enclosure.The partition 17 is secured to the top panel along a line 18 and issecured to the side panels 14 and along lines 19 and 20 respectively.

Similarly, the partition 18 is secured to the bottom panel 16 along aline 21 and. is secured to the side panels 14 and 15 along lines 22 and23 as shown. The rear panel 14 has an opening 24 formed at the lowersection thereof to make the enclosure open-ended.

Two speaker apertures shown in FIG. 1 are identified by referencenumerals 25 and 26. The aperture 25 is formed in the top panel 11 and isgenerally in line with a portion of the column which is defined by thepartition 17 and the front panel 12.

The aperture 26 is formed in the front panel 12 and is generallyperpendicularly oriented with respect to the aperture 25. The aperture26 is also perpendicularly oriented with respect to the column which isdefined by the front panel 12 and the partition 17 The details ofconstruction of the enclosure are not critical although the enclosureshould be generally sealed and the various members fastened together inaccordance with good acoustical design techniques.

The resulting enclosure defines a folded column which is generallyserpentine in configuration extending from the end which is adjacent tothe openings 25 and 26, around the partitions or baffles 17 and 18, tothe opening 24 in the rear panel 14.

The path length of the column is generally equal to one-quarter wavelength at the resonant frequency of the speakers which are to be mountedin the apertures 25 and 26. As explained, all inside surfaces of theenclosure should be treated with acoustically absorbing material toprevent spurious resonances or standing waves from developing within theenclosure.

Typical internal dimensions for a speaker enclosure such as that shownin FIG. 1 for a four inch diameter high compliance speaker mounted ineach of the apertures 25 and 26 would be as follows:

The length of the top panel 11 13% The width of the top panel 11 4%inches The height of the front panel l2 12 inches The length of thepartitions 17 and 18 7% inches The spacing between the partitions and 4%inches between the partitions and the rear and front panels.

In FIG. 2 the speaker enclosure of FIG. 1 is shown complete with soundabsorbing material and with a pair of high compliance, speakers mountedin the associated In addition, a further high compliance speaker 28 ismounted in the aperture 26. Both of the speakers 27 and 28 requireloading to operate effectively and both of these speakers utilize thesame tuned column of air provided by the serpentine or folded pathillustrated by the arrows identified by the numeral 29.

The speakers 27 and 28 are mounted so that their axes are perpendicularto one another and are both mounted at the same end of the tuned columnso that the effective path length from the respective speakers to theopening 24 at the rear of the enclosure is approximately one-quarterwave length of the in-air resonance of each of the speakers.

In the above way, improved power handling capability can be achievedwhile obtaining the important low frequency advantage of the highcompliance speaker and enclosure combination described in myaboveidentified co-pending application. In addition improved sounddispersal is obtained without increasing the volume of the speakersenclosure.

I claim as my invention:

1. In combination; a rigid acoustic enclosure having a series of panelsdefining an open-ended tuned column; sound absorptive means in saidcolumn, first and second high compliance loudspeakers having low naturalresonances, means mounting the first of said high complianceloudspeakers in one panel of said rigid acoustic enclosure adjacent oneend of said column, means mounting the second of said high complianceloudspeakers in another panel of said rigid acoustic enclosure alsoadjacent said one end of said column, the axes of said first and secondloudspeakers forming an angle approximately a right angle with oneanother, the mean path length of said column being chosen to augment thelow frequency response of each of said high compliance loudspeakers, andprovide substantial loading therefor, whereby said loudspeakers may beeffectively operated at frequencies well below the frequency of saidnatural resonance said column being folded and having a cross-sectionalarea which is approximately equal to the cross-sectional area of thecone of one of said high compliance loudspeakers.

2. The combination as set forth in claim 1 wherein said high complianceloudspeakers are mounted at right angles to each other.

3. The combination as set forth in claim 2 wherein said high complianceloudspeakers have substantially the same diameter.

4. The combination as set forth in claim 1 wherein said high compliancespeakers have substantially the same natural resonance.

5. The combination of first and second high compliance loudspeakers, anopen ended rigid acoustic enclosure having means defining a column foraugmenting the low frequency response of said high complianceloudspeakers, said rigid acoustic enclosure being formed of plane wallsarranged substantially at right angles to each other and beingacoustically lined, each of said high compliance loudspeakers beingmounted at adjacent angularly disposed walls at the same end of theenclosure, said column having a cross-sectional area which isapproximately equal to the cross-sectional area of the cone of one ofsaid high compliance loudspeakers, the mean path length of said columnbeing chosen to augment the low frequency response of each of said highcompliance loudspeakers and provide substantial loading therefor,whereby each speaker is operable at frequencies well below the in airresonance of said speakers.

6. The combination as set forth in claim 5 wherein 5 the path length ofsaid column is substantially onequarter wave length of a frequency whichapproximates the in-air resonance of said high compliance speaker.

* i i i

1. In combination; a rigid acoustic enclosure having a seriEs of panelsdefining an open-ended tuned column; sound absorptive means in saidcolumn, first and second high compliance loudspeakers having low naturalresonances, means mounting the first of said high complianceloudspeakers in one panel of said rigid acoustic enclosure adjacent oneend of said column, means mounting the second of said high complianceloudspeakers in another panel of said rigid acoustic enclosure alsoadjacent said one end of said column, the axes of said first and secondloudspeakers forming an angle approximately a right angle with oneanother, the mean path length of said column being chosen to augment thelow frequency response of each of said high compliance loudspeakers, andprovide substantial loading therefor, whereby said loudspeakers may beeffectively operated at frequencies well below the frequency of saidnatural resonance said column being folded and having a cross-sectionalarea which is approximately equal to the cross-sectional area of thecone of one of said high compliance loudspeakers.
 2. The combination asset forth in claim 1 wherein said high compliance loudspeakers aremounted at right angles to each other.
 3. The combination as set forthin claim 2 wherein said high compliance loudspeakers have substantiallythe same diameter.
 4. The combination as set forth in claim 1 whereinsaid high compliance speakers have substantially the same naturalresonance.
 5. The combination of first and second high complianceloudspeakers, an open ended rigid acoustic enclosure having meansdefining a column for augmenting the low frequency response of said highcompliance loudspeakers, said rigid acoustic enclosure being formed ofplane walls arranged substantially at right angles to each other andbeing acoustically lined, each of said high compliance loudspeakersbeing mounted at adjacent angularly disposed walls at the same end ofthe enclosure, said column having a cross-sectional area which isapproximately equal to the cross-sectional area of the cone of one ofsaid high compliance loudspeakers, the mean path length of said columnbeing chosen to augment the low frequency response of each of said highcompliance loudspeakers and provide substantial loading therefor,whereby each speaker is operable at frequencies well below the in airresonance of said speakers.
 6. The combination as set forth in claim 5wherein the path length of said column is substantially one-quarter wavelength of a frequency which approximates the in-air resonance of saidhigh compliance speaker.